Fuel cells are devices that can convert chemical energy directly into electrical energy through electrode reaction of hydrogen and oxygen. A fuel cell typically includes multiple fuel cell units. Each fuel cell unit includes two electrodes (anode and cathode) separated from one another by an electrolyte material. The fuel cell units are stacked in series to form a fuel cell stack. An electrochemical reaction occurs as appropriate reactants are supplied to each electrode, i.e., the fuel is supplied to one electrode and the oxidant is supplied to the other electrode, thereby creating an electrical potential difference between the two electrodes. As a result, electrical energy is generated.
The core of the fuel cell is the fuel cell stack. Two ways to supply reactant gases to the fuel cell stack are presently known in the art. The reactant gases are supplied through common manifolds located either inside the fuel cell stack or outside the fuel cell stack. When gases are supplied through the common manifolds inside the fuel cell stack, the battery needs to be sealed to prevent leakage of the reactant gases and coolant as well as the mixing of the fuel, the oxidant, and the coolant through the common manifolds.
Ballard Inc.'s U.S. Pat. No. 5,284,718 describes placing sealing structures on the membrane electrode assembly (MEA) having a dimension the same as that of the bipolar plates. The MEA has three inlet through-openings and three outlet through-openings. Grooves are formed around peripheries of the through-openings and edges of the MEA in which the sealing structures are disposed. However, this approach is not suitable for thinner membranes. Based on the disclosure therein, Chinese Patent No. ZL200580042454 describes a sealing structure circumscribing the MEA. This may solve the limitation on the membrane thickness; however, due to the low utilization efficiency of the proton exchange membrane, waste may be incurred.
Another approach is to place sealing structures on bipolar plates by forming grooves around the peripheries of common manifolds and edges of the bipolar plates. The sealing structures are then disposed in the grooves. One drawback of this approach is the increased requirements for the sealant. The sealant, if penetrating into the reaction zone in the gas diffusion layer, may result in an increase in the concentration polarization.
The conventional way to make MEA is to adhere an insulating strengthening material to both sides of the proton exchange membrane to increase the strength of the proton exchange membrane. However, this manufacturing process is very complicated and time-consuming, and thus is not suitable for mass production.